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Diffstat (limited to 'src/main/java/org/apache/commons/math3/fraction/ProperFractionFormat.java')
| -rw-r--r-- | src/main/java/org/apache/commons/math3/fraction/ProperFractionFormat.java | 231 |
1 files changed, 231 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math3/fraction/ProperFractionFormat.java b/src/main/java/org/apache/commons/math3/fraction/ProperFractionFormat.java new file mode 100644 index 0000000..3f74f16 --- /dev/null +++ b/src/main/java/org/apache/commons/math3/fraction/ProperFractionFormat.java @@ -0,0 +1,231 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.commons.math3.fraction; + +import org.apache.commons.math3.exception.NullArgumentException; +import org.apache.commons.math3.exception.util.LocalizedFormats; +import org.apache.commons.math3.util.FastMath; +import org.apache.commons.math3.util.MathUtils; + +import java.text.FieldPosition; +import java.text.NumberFormat; +import java.text.ParsePosition; + +/** + * Formats a Fraction number in proper format. The number format for each of the whole number, + * numerator and, denominator can be configured. + * + * <p>Minus signs are only allowed in the whole number part - i.e., "-3 1/2" is legitimate and + * denotes -7/2, but "-3 -1/2" is invalid and will result in a <code>ParseException</code>. + * + * @since 1.1 + */ +public class ProperFractionFormat extends FractionFormat { + + /** Serializable version identifier */ + private static final long serialVersionUID = 760934726031766749L; + + /** The format used for the whole number. */ + private NumberFormat wholeFormat; + + /** + * Create a proper formatting instance with the default number format for the whole, numerator, + * and denominator. + */ + public ProperFractionFormat() { + this(getDefaultNumberFormat()); + } + + /** + * Create a proper formatting instance with a custom number format for the whole, numerator, and + * denominator. + * + * @param format the custom format for the whole, numerator, and denominator. + */ + public ProperFractionFormat(NumberFormat format) { + this(format, (NumberFormat) format.clone(), (NumberFormat) format.clone()); + } + + /** + * Create a proper formatting instance with a custom number format for each of the whole, + * numerator, and denominator. + * + * @param wholeFormat the custom format for the whole. + * @param numeratorFormat the custom format for the numerator. + * @param denominatorFormat the custom format for the denominator. + */ + public ProperFractionFormat( + NumberFormat wholeFormat, + NumberFormat numeratorFormat, + NumberFormat denominatorFormat) { + super(numeratorFormat, denominatorFormat); + setWholeFormat(wholeFormat); + } + + /** + * Formats a {@link Fraction} object to produce a string. The fraction is output in proper + * format. + * + * @param fraction the object to format. + * @param toAppendTo where the text is to be appended + * @param pos On input: an alignment field, if desired. On output: the offsets of the alignment + * field + * @return the value passed in as toAppendTo. + */ + @Override + public StringBuffer format(Fraction fraction, StringBuffer toAppendTo, FieldPosition pos) { + + pos.setBeginIndex(0); + pos.setEndIndex(0); + + int num = fraction.getNumerator(); + int den = fraction.getDenominator(); + int whole = num / den; + num %= den; + + if (whole != 0) { + getWholeFormat().format(whole, toAppendTo, pos); + toAppendTo.append(' '); + num = FastMath.abs(num); + } + getNumeratorFormat().format(num, toAppendTo, pos); + toAppendTo.append(" / "); + getDenominatorFormat().format(den, toAppendTo, pos); + + return toAppendTo; + } + + /** + * Access the whole format. + * + * @return the whole format. + */ + public NumberFormat getWholeFormat() { + return wholeFormat; + } + + /** + * Parses a string to produce a {@link Fraction} object. This method expects the string to be + * formatted as a proper fraction. + * + * <p>Minus signs are only allowed in the whole number part - i.e., "-3 1/2" is legitimate and + * denotes -7/2, but "-3 -1/2" is invalid and will result in a <code>ParseException</code>. + * + * @param source the string to parse + * @param pos input/ouput parsing parameter. + * @return the parsed {@link Fraction} object. + */ + @Override + public Fraction parse(String source, ParsePosition pos) { + // try to parse improper fraction + Fraction ret = super.parse(source, pos); + if (ret != null) { + return ret; + } + + int initialIndex = pos.getIndex(); + + // parse whitespace + parseAndIgnoreWhitespace(source, pos); + + // parse whole + Number whole = getWholeFormat().parse(source, pos); + if (whole == null) { + // invalid integer number + // set index back to initial, error index should already be set + // character examined. + pos.setIndex(initialIndex); + return null; + } + + // parse whitespace + parseAndIgnoreWhitespace(source, pos); + + // parse numerator + Number num = getNumeratorFormat().parse(source, pos); + if (num == null) { + // invalid integer number + // set index back to initial, error index should already be set + // character examined. + pos.setIndex(initialIndex); + return null; + } + + if (num.intValue() < 0) { + // minus signs should be leading, invalid expression + pos.setIndex(initialIndex); + return null; + } + + // parse '/' + int startIndex = pos.getIndex(); + char c = parseNextCharacter(source, pos); + switch (c) { + case 0: + // no '/' + // return num as a fraction + return new Fraction(num.intValue(), 1); + case '/': + // found '/', continue parsing denominator + break; + default: + // invalid '/' + // set index back to initial, error index should be the last + // character examined. + pos.setIndex(initialIndex); + pos.setErrorIndex(startIndex); + return null; + } + + // parse whitespace + parseAndIgnoreWhitespace(source, pos); + + // parse denominator + Number den = getDenominatorFormat().parse(source, pos); + if (den == null) { + // invalid integer number + // set index back to initial, error index should already be set + // character examined. + pos.setIndex(initialIndex); + return null; + } + + if (den.intValue() < 0) { + // minus signs must be leading, invalid + pos.setIndex(initialIndex); + return null; + } + + int w = whole.intValue(); + int n = num.intValue(); + int d = den.intValue(); + return new Fraction(((FastMath.abs(w) * d) + n) * MathUtils.copySign(1, w), d); + } + + /** + * Modify the whole format. + * + * @param format The new whole format value. + * @throws NullArgumentException if {@code format} is {@code null}. + */ + public void setWholeFormat(NumberFormat format) { + if (format == null) { + throw new NullArgumentException(LocalizedFormats.WHOLE_FORMAT); + } + this.wholeFormat = format; + } +} |